I stumbled across miscibility curves in the section Solubility of Liquids in Liquids (Organic Chemistry, by Wallwork and Grant) today. I'm not sure if my problem is with the way the content was laid out in the book or whether I'm not fully understanding the material, but I feel the book has dealt with the topic in a rather, obscure way.
I've taken snapshots of it and uploaded a portion of my text below.
What I want to know is if I interpreted the text (the bit about miscibility curves) correctly, which I seriously doubt.
Here's my interpretation:
This is the miscibility curve for phenol in water blah-blah-blah. All the points present in the area bound by the curve with the x-axis (concentration axis) are points of immiscibility. The curve itself represents the threshold of miscibility.
For example, at 20°C, phenol is soluble in water up till the concentration corresponding to point A on the curve. However, for phenol concentrations corresponding to points between A and B (lying on the line AB), the phenol-water mixture is immiscible and the phenol and water form separate layers. Although, at concentrations corresponding to point B (and beyond), the phenol is completely soluble. When for a constant temperature, the miscibility curve maps to two concentrations on the x-axis (eg; points A and B in the graph), which represent thresholds of miscibility at that temperature, the two mixtures (i.e- at A and B) are called conjugate pairs.
I labored for over two hours to come to the above conclusion, but when I saw the portion of the text which mentions that the liquids A and B exist together (at equilibrium) for the given temperature, I had to throw in the towel.
I have a very strong feeling that a large part of my 'interpretation' is horribly incorrect. If anyone's got the time, could you explain what the text actually means?